Centaurea diffusa
Diffuse knapweed
Family: Asteraceae · Type: Herb · Not Native
Conservation status: Cal-IPC Yes
Centaurea diffusa (Diffuse knapweed) is a non-native California herb in the Asteraceae family, recognized by creamy white flowers, much-branched habit, and 2-pinnately divided leaves.
Diffuse knapweed is a naturalized perennial herb found in northwestern California, the Cascade Range, northern and central Sierra Nevada, Sacramento Valley, San Francisco Bay Area, southern Coast Ranges, San Bernardino Mountains, and Modoc Plateau in fields, roadsides, and open woodlands at elevations below 2,300 meters. Flowering from May to October, this plant produces creamy white to lavender flowers in heads 10 to 13 millimeters long, arranged in open panicle-like clusters. Growing with much-branched stems 20 to 80 centimeters tall that are puberulent and grayish-tomentose, it develops a complex branching structure. Its leaves are distinctively divided, with basal and lower stem leaves 10 to 20 centimeters long, deeply 2-pinnately divided into linear to oblong lobes, while upper stem leaves become progressively less divided. The plant's distinctive involucre features pale green phyllaries with prominent parallel veins and fringed appendages ending in straw-colored spines 1 to 3 millimeters long.
Identification and appearance
Key characters: 14 sympatric species; creamy white flowers, much-branched habit, and 2-pinnately divided leaves are diagnostic
Habitat and range
Habitat: Fields, roadsides, open woodland
Elevation: < 2300 m
Outside California: North America, native to southeastern Europe
Bloom period
Centaurea diffusa blooms May-Oct.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Cirsium: Cirsium bracts taper to simple spines; Centaurea bract tips expanded with fringed/toothed edges; vs Carduus: Carduus bracts spine-tipped but not fringed; Centaurea bract appendages distinctly fringed or toothed; vs Jacobaea: Jacobaea has obvious yellow ray flowers; Centaurea lacks true rays (all tubular flowers); vs Silybum: Silybum has white-veined leaves and simple spine-tipped bracts; Centaurea bracts ornately fringed; vs Eriophorum: Eriophorum is a sedge with grass-like leaves and cottony heads; Centaurea is a branched herb
Frequently asked questions
Is Centaurea diffusa native to California?
No. Centaurea diffusa is not native to California (recorded as not native).
When does Centaurea diffusa bloom?
Centaurea diffusa blooms May-Oct.
What plant family does Centaurea diffusa belong to?
Centaurea diffusa is in the Asteraceae family, genus Centaurea.
Is Centaurea diffusa invasive in California?
Centaurea diffusa is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Centaurea diffusa grow in?
Centaurea diffusa grows in Fields, roadsides, open woodland.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.